1. Field of the Invention
The present invention relates to an extrusion-molding machine, an extrusion-molding method, and a method for manufacturing a honeycomb structured body.
2. Discussion of the Background
In recent years, particulates such as soot contained in exhaust gases that are discharged from internal combustion engines of vehicles, such as buses and trucks, and construction machines, have raised serious problems as contaminants harmful to the environment and the human body.
Various honeycomb filters using honeycomb structured bodies made from porous ceramic materials, which serve as filters that capture particulates in exhaust gases to purify the exhaust gases, have been proposed.
Conventionally, upon manufacturing a honeycomb structured body, first, ceramic powder serving as material powder and a binder are dry-mixed, and to this is further added a dispersant solution and the like, and mixed so that a wet mixture is prepared. Moreover, the wet mixture is continuously extrusion-molded through a die, and the extruded molded body is cut into a predetermined length so that a pillar-shaped honeycomb molded body is manufactured.
Next, the resulting honeycomb molded body is dried by using a microwave drying apparatus or a hot-air drying apparatus, and after the honeycomb molded body thus dried has been again cut into a precise length, predetermined cells are sealed so as to manufacture a honeycomb molded body in which one of ends of each cell is sealed with a plug material layer. Thereafter, a degreasing process is carried out on the resulting honeycomb molded body, and then a firing process is carried out on the degreased honeycomb molded body placed on a firing jig so that a honeycomb fired body is manufactured.
Next, after attaching a gap holding member to each of the side faces of the honeycomb fired body, a sealing material paste is applied thereon, and a number of honeycomb fired bodies are bonded to one another by interposing sealing material layers (adhesive layers), with the honeycomb fired bodies mutually bonded to one another with an interval formed by the gap holding member, so that an aggregate of the honeycomb fired bodies is manufactured. Next, the resulting aggregate of the honeycomb fired bodies is cut and machined into a predetermined shape, such as a cylindrical shape and a cylindroid shape, by using a cutting tool or the like so as to form a ceramic block, and lastly, a sealing material paste is applied onto the periphery of the ceramic block to form a sealing material layer (coat layer); thus, manufacturing of the honeycomb structured body is completed.
In the above-mentioned manufacturing process, upon manufacturing the honeycomb molded bodies, the resulting molded bodies need to have a uniform composition. For this reason, normally, after dry-mixing the ceramic powder and a binder as described above, the powder mixture and a liquid-state dispersant solution are mixed by using a mixing apparatus, and then again mixed using an extrusion-molding machine provided with a screw, and further extrusion-molded through a die.